Dr. Marvin Rowe, and his chemistry graduate students at Texas A&M University developed and pioneered the plasma oxidation technique to directly date pictographic rock art. Using samples collected mainly from 41VV75 in Seminole Canyon State Park and Historic Site
Originally, radiocarbon dating was done by measuring that β– emission. However, a more sensitive technique is now available to analyze smaller samples by directly measuring the ratio of C-14 that remains in a sample and the stable isotopes of carbon, using a technique called accelerator mass spectrometry.
One beneficial aspect of plasma oxidation over other sample preparation techniques is that only the organic carbon is extracted, leaving intact the inorganic portion of the paint sample because the system remains below the decomposition temperature of these minerals. This allows us to avoid the extensive acid treatments that traditional sample preparation and combustion use. And, we are able to analyze much smaller samples with high mineral content, which is ideal for dating paint that is still adhering to rock! Once the carbon dioxide is extracted, it is sent for radiocarbon dating using AMS. I have collaborated with Lawrence Livermore National Laboratory’s Center for Accelerator Mass Spectrometry (CAMS) for over 20 years.
In the 1990s my former graduate advisor, Dr. Marvin Rowe, and his chemistry graduate students at Texas A&M University developed and pioneered the plasma oxidation technique to directly date pictographic rock art. Using samples collected mainly from 41VV75 in Seminole Canyon State Park and Historic Site, Marvin and his graduate students utilized the plasma oxidation method to extract the organic binders and emulsifiers in the paint. These samples from 41VV75 became some of the first directly dated pictographs anywhere in the world! When I took the position as Research Director, I knew that I would be establishing a Shumla Chemistry Laboratory. The first instrument I built was a plasma oxidation system so Shumla could begin preparing paint samples for radiocarbon dating. I’ve made some changes to Marvin’s original design, but the basic principal remains the same: employ plasma oxidation of the organic binders/emulsifiers in the paint layer to extract organic material for radiocarbon dating.
“We call the process Low Energy Plasma Radiocarbon Sampling,” said New Mexico’s state archeologist Eric Blinman, who credits Rowe with inventing the process. “But a lot of people just refer to this as ‘Marvin’s Machine.’”
The plasma oxidation technique was made to date the organic materials used in rock paintings.
But it has been found that it can also be used for dating other types of organic artifacts, like
bones and wood, without significant differences in the results.
Looking for Time in a Glowing Bottle How plasma is changing the game of dating archaeological artifacts. The “glowing bottle” of plasma dating; photograph courtesy the